Method of strengthening and improving cast iron



TUNITED STATE s] PATENT I OFFICE METHOD OF STRENGTHENINGAND IMPROVING CAST IRON John C. Martino, Cicero, Ill.

No Drawing. Application April 24, 1941, Serial No. 390,112

. 2 Claims. (ems-57) s This invention relates to a treatment of gray cast irons and malleable cast irons in the stage shortly after their removal from the melting unit or medium.

Objects of the invention are to strengthen the metal, reduce porosity, eliminate shrinkages and improve the micro structure of the finished prod-4 uct. I

Another object is to lower. the combined carbon in the metal, of a given analysis.

Another object is to raise the freezing temperature of the metal, which'limits the need for heavy risers and other external means for the feeding of a casting.

in a fine configuration. This produces a cast iron which is stronger throughout and with resultant greatly increased transverse and tensile strength. I have found" that where carbide stabilizing elements, such as chromium and molybdenum Other objects, advantages and-capabilities of the invention will later more fully-appear.

I add to the molten metal fractional percentages of approximately one-fifth of one per cent by weight of one or a combination of the solid hydrocarbons of the methane series, such as paraffin; fatty acid derivatives of the higher hydrocarbon series, such as stearic acid; derivatives composed chiefly of glycerol and fatty acid esters such as fats, and alcohol and fatty acid esters such as beeswax and spermacetti, shortly after its removal from the melting unit or medium.

While I have referred to one-fifth of one per cent as being satisfactory, I do not want to be limited to that exact percentage as otherpercentages may give satisfactory results within the limits of my invention. I have found that considerable variation of the percentage is permissible, and only refer to one-fifth of one per cent as giving satisfactory results. After the flaming ceases, which flaming may last from to seconds,

the treated metal is ready to be poured into the mold. For. example, I have added to gray cast iron approximately one-fifth of one .per cent by weight of parafiin Wax with satisfactory results. I have also used spermacetti in the same proportion with satisfactory results. Also I have used stearic acid in the proportion of seventeen I invention.

hundredths of one per cent with decidedly beneflcial results,- I

In the commercial application of my invention, I have found that the cast iron so treated has less porosity with resultant reduction in shrinkage and spongine'ss of the metal. The resultant macro-structure is finerand denser, markedly tending to be more uniform throughout a given cross section of casting, and the graphite being are not used the increase in strength by reason of my invention is very substantial, the transverse strength being increased approximately twenty-five per cent and the tensile strength being increased substantially twenty-dive per cent or more. Where such carbide stabilizing elements as chromium and the like are used, the increase in strength is not quite so much, but the product so treated by my method shows amarked refinement in grain structure.

It is to be noted that the application of my improved method produces results similar to cast irons containing added alloys, such as nickel, copper and chromium, which is important at the present time inasmuch as they are more or less defense items and consequently are scarce and diflicultto obtain.

I have observed in the practice of my method that there is a considerable reduction in shrinkage, largely eliminating porosity and cavities. The result is that it is feasible to reduce the size of risers used in the feeding ofa casting in a n.0ld, and in some instances the number of risers required is reduced. There is an obvious saving of metal used in the pouring of a casting and also a saving in the amount of sprue to be removed after the casting is completed.

Although the invention has been disclosed in I connection with the specific details of preferred embodiment thereof, I wish it understood that such details are not intended to be limitive of the Having now described my invention, I claim: 1. The method of substituting in molten cast iron shortly after it leaves the melting unit, a

, fractional percentage of less than one per cent of solid hydrocarbons of the series from CzoHa to C2'zH5s for chromium, nickel and other alloys in order to strengthen the cast iron.

2. The process of strengthening and improv- I ing molten cast iron by adding thereto approximately one-fifth of one per cent by weight of the wax spermacetti in order to strengthen the cast iron.

JOHN .C. MARTINO. 

